Saw regrinding machines such as top and face grinders are used for sharpening the teeth of circular saw blades. Typically such machines rotate a saw blade in increments stopping each tooth of the blade at a position where a grinding wheel may grind the appropriate surface of the tooth. An automatic saw sharpener of this type requires very precise positioning for the grinding wheel to execute a grinding stroke. Typically there is an indexing mechanism which includes a finger interposed into the path of the blade to intercept each tooth at a particular location in space as the blade is rotated after each sharpening stroke. An example of a saw blade top and face grinder which includes an indexing apparatus of this type is shown in my U.S. Pat. No. 5,038,639 entitled SAW BLADE TOP AND FACE GRINDER issued Aug. 13, 1991.
The aforementioned patent, the text of which is incorporated herein by reference, illustrates a top and face grinding machine that includes an indexing apparatus which imposes a stop into the path of the teeth of the saw blade from a position which is laterally displaced from the plane of the saw blade. The saw blade is rotated incrementally in a clockwise direction to advance the next tooth to be ground, and then counterrotated in a counterclockwise direction to precisely position the tooth. It is during the counterclockwise rotation that the index finger is interposed into the path of the plane of the saw blade to intercept the particular tooth that is to be sharpened. Once the finger stops the counter-rotating saw blade at the correct position for sharpening, a side clamping mechanism is engaged which holds the saw blade in a stationary position for the grinding stroke. At this point the index finger is moved out of the way.
The indexing mechanism of the aforementioned '639 patent suffers, however, from several drawbacks. It is a relatively complicated mechanism, both in the manner of its operation, and in the expense associated with the number of parts that must be machined and assembled.
A desirable objective would be to provide an indexing stop that could be interposed into the plane of the blade from a lateral position, but without the attendant complexity and fabrication expense of the aforementioned system.
Another problem that is common to contemporary automatic saw regrinding machines is the necessity for coordinating the various mechanical operations that must take place to advance the saw blade and regrind each tooth in turn. Pneumatic systems in particular are problematical because typically such systems include a multiplicity of air cylinders, each having its own pneumatic source which must be controlled by multiple valving arrangements actuated at the appropriate times. Such systems are complex and are prone to numerous adjustment problems.